Alternating current system



Sept. 8, 1931. w. HAHNEMANN ETAL 1,322,439

ALTERNATING CURRENT SYSTEM Original Filed March 17, 1928 #so mA-WWW, B

ma mi f Patented Sept. 8, 1931 UNITED STATES PATENT OFFICE WALTER HAHN'AEMANN, OF BERLIN-MARIENELDE, GERMANY, AND KARL BATH, 0l'

NEW YORK, N. Y.,.ASSIGNORS TO C; LORENZ AKTIEN GESELLSCHAFT, OF BERLIN- ALTERNATING CURRENT SYSTEM r'iginal Vapplication This application which is a division of l.application Serial No. 262,461 to Karl Schmidt, lV'alter Hahnemann and Karl Rat-li, filed March 17, 1928, refers to alternating current electrical systems and is more particularly directed to such systems in which a current of a given frequency is to be introduced into a circuit system carrying currents ofa different frequency, such as for instance, as is the case in a carrier current transmission over alternating current power lines for communication or distance control purposes.

The object of this invention is to .provide coupling meanswhereby a carrier current may be introduced into a power system without reaction of the comparatively heavy power currentsupon the delicate carrier current equipment.

Another object of this invention is to provide simple and effective means for producing a plurality of carrier currents introduced upon the power system by means of a single basicv carrier frequency.'

These and further objects ofi-our invention in detail of construction and operation,

will become apparent as the following detailed description proceeds,'which is taken in conjunction with the appended drawings showing by way'of example two circuit diagrams embodying our invention. It is understood that we do not wish to be limited to the practical examples as l.shown by the views of the drawings but that our invention is subject to many modifications coming within the broad spirit and scopeof the appended claims.

y igure 1 of the drawings shows an arrangement for`introducing two or more intermediate frequencies into the same power -line by using a single basic carrier freled March 17, 1928, Serial No. 262,461, and in Germany January 31, 1928. Divided and vthis application led June 17, 1929. Serial No. 371,597.V

purpose of communication or distant control and the like. In electrical power networks, it is often desirable to effect switching movements at distant points of the network, for instance at consuming points from the generating station, sub-station For this purpose, it has beenlproposed to use currents of an intermediate 1 or the like.

frequency which are superimposed upon the power line and which` serve to actuate a relay at the distant pointz e. g., a frequency relay. Thus, by employing several such currents of different frequencies, different distant controlling movements may be effected. For instance, such distant control may serve to adjust electricity meters'at the consumin points to different tariffs in accordance wit the loading period of the power station, or they may serve to directly switch in or out distant consumers such as street lighting ap aratus and the like. This invention has re erence to all such arrangements where a distant control or signaling along power lines is required.

Furthermore,rcarrier currents of this type are used for communication purposes, such as telephone conversations.

The main difliculty which arises in systems of this kind consists in comparatively strong power currents entering e into the more delicate carrier current apparatus, such as signalling and control equipment.

Anumber of means have been proposed in order to prevent this drawback, such as compensating circuit arrangements or the use of blocking or rejector circuits and the like. All these improvements have been very ineffective in that compensating circuits are very difficult to adjust and to operate and in that the use of blocking or rejector circuits aiford heavy and expensive electrical apparatus, such as condensers which render installation of this kind prohibitive in practice.

In the above mentioned application, a very simple and effective means has been proposed to overcome the above disadvantages. This consists in its broadest terms, in using an inductive coupling device having primary and secondary windings moving rela.-

tive to each other with a synchronous speed in respect to the power frequency. In this manner, couplin in respect to the power current, is abso utely prevented, whereas .for the carrier currents -having a different frequency, Van effective coupling connection is maintained. The most simple means of such-amoving 4inductive connection, consi'sts in the use of a synchronous machine such as a synchronous motor or generator,

whereby the carrier currents are introduced,

into the existing or into an auxiliary exciting` winding of the machine. l

According to the present invention, this phenomenon is made use of toproduce two or vmore signalling or controlling frequencies l,for transmitting differentl signals vforefecting different distant controls. When yzu chronous machines. The-exciting currents of these machines are taken out of the power line and are lof a frequency which has already'been nerated by the preceding machine. For t is purpose, well-known filtermgnitrecuits may be employed.

ad of using several machines, a single machine may be provided to produce any number of f uencies. The side or sp it frequencies pro uced in the stator are ...a reintroduced into the exciter, winding of thesame machine for the purpose of produc- 4ing further side frequencies, each differing by the amount of the' power frequency (50 cycles) from the plreceding exciting frequency. Thus, eac further transfer be- -tween exciter winding and armature as deaired will produce a new splitting up of the rectivefrequency.

- ferring to Fig. 1, T1 and T2 represent tw o transformers arranged in a single phase N. ZM1,'ZM2, ZM3 and ZM* are additional synchronous generators, whose Irotating field windings are' designated by `R1, R R, and R4 respectively.'` These are connected to, a source of exciting current such as a battery B. The exciting circuit of the machine ZM, includes an intermediate frequency alternator MG providing, e. g., an

initial frequency of 500 cycles. Thus, in thel armature winding of ZM., two frequencies will'be produced of 450 and 550 cycles respectively. These may be employed to transmit two different signals or to effect two differ- .ent distant controls. Both these frequencies are furthermore employed to excite, in a manner similar to machine MG, two additional machines ZM1 and ZM2 respectively. To this end, a transformer T, is provided, with its primary connected to the network,

f and its secondary connected to the exciting circuits of machine ZM1 and ZM,. Each of these exciting circuits of machines ZMl and ZMz is inseries with filter circuits containing an inductance and capacity in series tuned to the respective frequency. In this 7 manner, lfour further frequencies will be obtained in the qpwer line, 1. e., 400, 500 c cles from one mac ine and 500, 600 cyclesom the other. These frequencies in their turn may be employed for the excitation of further synchronous machines. In the example shown, a further machine ZM. is added, which has an exciting current of 400 cycles superim o sed on the direct current excitation. us, by an arran ement represented 9 by Fig. 1, six different requencies ranging from 350 to 600 cycles in steps of 50 cycles will be obtained. AM is a common synchronous motor driving the additional machines ZM1 to ZM.. Also synchronous motors may be employed, as has a ready been stated above.

According tol the arrangement of Fi 2, a single machine is provided for the r uction of any number of frequencies. imilar 9 reference characters refer to similar parts as in Fig. 1.- The exciting circuit of the auxiliary generator includes again a 500 cycle current source MG. Moreover, there 1s a number of filter circuits arranged in parallel 95 and tuned to the different frequencies taken from the vline and intended to supply the exciting circuitof the s chronous machine. At first, two fr uencies of 450 and 550 cycles will be obtained out of the 500 cycles 10 fundamental frequency which are reintroducedinto the exciter`A winding of the same machine. These respective frequencies are then decomposed again. In the case shown,

lthis splitting up is carried out for a frequency band ranging from 350 to 700 cycles in steps of 50 cycles. For this purpose, there are six filter circuits tuned as indicated by numerals in the drawings which must. be provided, as maybe readily understood.

Instead of superimposing theintermediate frequencies upon the main exciter winding of this machine, special' exciter windings. may be -provided for each or all of the intermediate uencies. y Having disclosed lthe principle of vour invention, various modifications will .be apparent to those skilled in the art. Our in- Y ventiontherefore, is not limited to the specie. disclosure, but only by the scope 'ofy the 15 l following claims v 1. In combination with an electrical carrier current Y system .for alternating current power lines carrying current of predetermined frequency, ,means to vproduce and introducel a plurality of carrier currents of different frequencies into said power line, said means comprising a coupling device having primary and secondary windings moving relative to each other in synchro- 130 nism with said power frequency, a source of carrier current of definite. frequency, means to introduce said carrier current into said primary winding, means for picking out at least one of split frequencies of said carrier frequency produced in said power line through said coupling device, and means for resplitting and reintroduciiig said split frequency.

lo .2. In combination with an electrical car- .rier current system for alternating current power lines carrying current of definite power frequency, means for producing and introducing a plurality of carrier currents of diiferent frequencies into said power line, said means comprising a synchronous device having primary and secondary windings moving relative to each other in synchronism with said power frequency, a source of carrier current of a fundamental frequency, means to apply said carrier current to the primary winding of said device, means for picking current of a split frequency of said carrier frequency produced in said system through said device, and further means for reintroducing and resplitting said current of said last frequency.

3. In combination with an electrical carrier current system for alternating current power lines carrying current of definite power frequency, means for producing and introducing a plurality of carrier currents of different frequencies into the power line, said means comprising a synchronous machine having a stator winding and a rotor exciter winding rotating synchronously in respect to said stator field, a source of carrier current of basic frequency, means to apply current derived from said source to said rotor exciter winding, means to consecutively pick out, resplit and reintroduce currents of split frequencies of said basic frequency produced in said power line through said synchronous machine.

4. In combination with an electrical system carrying current of definite frequency, means to introduce current of different fre quency into said system, said means comp'rising inductive coupling windings moving relative to each other in synchionisin with said definite frequency, and means for rei'zitroducing currents of split frequencies of said different frequency produced in said system through said coupling windings.

5. In combination with an electrical carrier current system for power lines carrying current of definite power frequency, means for producing and introducing a plurality of currents ofdifferent carrier frequencies into the power line, said means comprising a synchronous machine connected to said power line, an exciter winding for said machine, a source of carrier current of a basic frequency, means to supply currents from c5 said source to said exciter winding, and

further means including filter circuits for consecutively picking out, resplitting and reintroducing vcurrents of split frequencies produced from said carrier current into the power line through said synchronous machine.

6. In combination with a network carrying currents of a predetermined frequency, means for introducing into said network a plurality of currents having frequencies different from said said means comprising a synchronous machine having an exciter circuit, a generator producing a current of a frequency different from said predetermined frequency included in said exciter circuit, and independent means for introducing currents of other split frequencies fiom said network to Said exciter circuit.

7 In combination with a network carrying currents of a predetermined frequency, means for introducing into said network a plurality of currents having frequencies different from said predetermined frequency, said means comprising a synchronous machine having an exciter circuit, a generator producin a current of a frequency different from sai predetermined frequency included in said exciter circuit, whereby currents of two split frequencies are superimposed on the network and means including circuits resonant to said superimposed split frequencies for reiiitroducing currents of said split frequencies into said exciter circuit.

8. In combination with a network carrying currents of a predetermined frequency, means for introducing into said network a pluralit of currents having frequencies different fi-om said predetermined frequency, said means comprising a synchronous` machine having an exciter circuit, a generator producing a current of a frequency different from said predetermined frequency included in said exciter circuit whereby two split frequencies are superimposed upon said network, other exciter circuits for said synchronous machine, and means for reintroducing currents of said split frequencies from said network into said other exciter circuits.

In testimony whereof we affix our signatu res.

WALTER HAHNEMANN. KARL BATH.

redetermined frequency,

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